The present invention is directed to a hand-held multiple channel liquid transfer device and more specifically to a multiple channel transfer device utilizing a plurality of plungers in combination with an elastic diaphragm adapted to be stretched by the plungers into each channel.
Many tests and applications in the medical field require picking up predetermined amounts of liquid reagents from one container and injecting or depositing the same into another recepticle or container as a daily or routine bench procedure. An example of such a test is one performed in a multi-well micro tube tray where a culturing/rehydrating medium is added to a dried prepared micro-tube tray to perform an antibiotic sensitivity test or bacterial identification. Another example is in hybridoma screening and cloning where the same type of multi-well plate containing cells has to be fed with fresh growth media periodically and/or, when determined, the cells themselves are transferred to another plate or receptacle for further studies.
In the past pins or prongs such as disclosed in the U.S. Pat. No. 2,956,931 to Goldberg or loops as disclosed in the U.S. Pat. No. 4,115,200 to Anderson were used for picking up small drops by surface tension and depositing them in another solution. The amount of liquid transferred by such means is generally limited and such means basically carry out a mixing operation because they take out the same volume they put in. The risk of contamination is high if not sterilized between uses due to the contact of the prong or loop with the various mixtures in the containers. These drawbacks can be overcome by a positive displacement device such as a syringe. However, syringes generally require the use of O-rings or other close tolerance type seals which provide resistant to movement making them hard to operate when grouped into a multi-channel battery. Furthermore, the use of syringes in a multi-channel hand-held transfer device are apt to be trouble prone, easily contaminated, expensive or bulky.
The U.S. Pat. No. 3,982,438 to Byrd discloses a multiple sample pipetting apparatus wherein a plurality of small tubes extend downwardly with the upper end portions communicating with reservoirs that have a predetermined volume. A flexible diaphragm extends across all of the reservoirs and the upper ends thereof are in communication with a common manifold chamber. The application of positive or negative pressure moves the diaphragm downwardly and upwardly into contact with the lower and upper reservoir walls respectively to either extract or expel liquid from the tubes. The accuracy of the amounts of liquid extracted or expelled by the tubes is dependent upon the pressure in the manifold chamber and the volume thereof and does not rely upon the use of reciprocating plungers.
The U.S. Pat. No. 3,568,735 to Lancaster discloses a laboratory microtritation dispensing apparatus comprising a manifold connected to a plurality of passageways, a head member connected to the manifold and having a plurality of apertures aligned with the passageways but separated therefrom by a flexible diaphragm, an actuator mounted in each aperture including a piston normally biased by a spring to maintain the flexible diaphragm means out of its respective one of said apertures and a dispensing needle connected to each actuator assembly whereby upon supplying and exhausting air to and from the manifold, the diaphragm will be moved by the differential pressure on opposite sides thereof to operate the pistons in the respective apertures to control the pickup and discharge of fluid by the needles. Thus, Lancaster utilizes air pressure in the manifold for controlling the transfer of liquids as does the patent to Byrd.
The U.S. Pat. No. 4,047,438 to Sekine discloses a liquid quantitative dispensing apparatus for withdrawing liquid into a plurality of pipettes arranged in rows by simultaneously pressing and releasing cap-like projections formed of flexible material and dispensing the liquid to test tubes and the like. The cap-like projections of flexible material are disposed in alignment with a plurality of pipettes and extend upwardly into bores in a guide plate. A plurality of plungers secured to a common plate are operative within the bores for pressing on the cap-like projections to dispense the liquid from the pipettes. In this patent, as well as the two previously mentioned patents, it is extremely difficult to provide a good seal for the membrane since the membrane is being clamped between two flat surfaces.